‘Slow sites convert worse’ has been repeated so often it starts to sound like a platitude, but the underlying data is more specific and more actionable than the one-liner suggests.
What the research actually shows
Studies from Google and various CRO firms have consistently found conversion rates drop sharply as load time crosses the 2 to 3 second mark, and bounce rate climbs in roughly the same window. The exact numbers vary by industry, but the direction is never in dispute: speed is not a nice-to-have, it is a revenue lever.
The usual culprits
- Unoptimized images — a single uncompressed hero image can outweigh the rest of the page combined.
- Render-blocking CSS and JavaScript — scripts that force the browser to wait before it can show anything.
- No caching — rebuilding the same page from scratch for every single visitor.
- Plugin sprawl — each one adds its own scripts and stylesheets, whether or not the page actually needs them.
The practical fix
You do not need to solve all of this by hand. A good caching and optimization layer (we typically deploy WP Rocket for WordPress clients) handles image optimization, minification, and caching automatically, and it is usually the single highest-leverage change you can make to an existing site in one afternoon.
We will be publishing a full before-and-after breakdown from one of our recent projects soon — the numbers are a genuinely convincing argument on their own.